Abstract

Mitigation—preventative actions to reduce the human forcing of climate change with the goal of keeping climate change within a range to which humans can adapt—must be prompt, rigorous, and focused on eliminating emissions of carbon dioxide, beginning with rapid cessation of the use of coal. Carbon dioxide is by far the most threatening greenhouse gas because it remains in the atmosphere for millennia longer than any other major greenhouse gas, and the heat retained on the planet by atmospheric carbon dioxide will continue to emerge from its transitional storage in the deep oceans for millennia after the atmospheric carbon finally dissipates. Sustainable development can be increased and ocean acidification can be stopped only if the dominant fossil fuel regime is promptly replaced by an affordable and accessible alternative energy regime. Poorer countries cannot be reasonably expected to cooperate with vigorous mitigation unless they are assisted with necessary adaptation.